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    SubjectRe: [PATCH 5/6] Try using new kvm clock msrs
    On Mon, Apr 26, 2010 at 01:46:27PM -0400, Glauber Costa wrote:
    > We now added a new set of clock-related msrs in replacement of the old
    > ones. In theory, we could just try to use them and get a return value
    > indicating they do not exist, due to our use of kvm_write_msr_save.
    >
    > However, kvm clock registration happens very early, and if we ever
    > try to write to a non-existant MSR, we raise a lethal #GP, since our
    > idt handlers are not in place yet.
    >
    > So this patch tests for a cpuid feature exported by the host to
    > decide which set of msrs are supported.
    >
    > Signed-off-by: Glauber Costa <glommer@redhat.com>
    > ---
    > arch/x86/kernel/kvmclock.c | 56 +++++++++++++++++++++++++++----------------
    > 1 files changed, 35 insertions(+), 21 deletions(-)
    >
    > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
    > index feaeb0d..f2f6aee 100644
    > --- a/arch/x86/kernel/kvmclock.c
    > +++ b/arch/x86/kernel/kvmclock.c
    > @@ -29,6 +29,8 @@
    > #define KVM_SCALE 22
    >
    > static int kvmclock = 1;
    > +static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
    > +static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
    >
    > static int parse_no_kvmclock(char *arg)
    > {
    > @@ -41,6 +43,7 @@ early_param("no-kvmclock", parse_no_kvmclock);
    > static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
    > static struct pvclock_wall_clock wall_clock;
    >
    > +

    Extra newline.

    > /*
    > * The wallclock is the time of day when we booted. Since then, some time may
    > * have elapsed since the hypervisor wrote the data. So we try to account for
    > @@ -54,7 +57,8 @@ static unsigned long kvm_get_wallclock(void)
    >
    > low = (int)__pa_symbol(&wall_clock);
    > high = ((u64)__pa_symbol(&wall_clock) >> 32);
    > - native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
    > +
    > + native_write_msr_safe(msr_kvm_wall_clock, low, high);
    >
    > vcpu_time = &get_cpu_var(hv_clock);
    > pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
    > @@ -130,7 +134,8 @@ static int kvm_register_clock(char *txt)
    > high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
    > printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
    > cpu, high, low, txt);
    > - return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
    > +
    > + return native_write_msr_safe(msr_kvm_system_time, low, high);
    > }
    >
    > #ifdef CONFIG_X86_LOCAL_APIC
    > @@ -165,14 +170,15 @@ static void __init kvm_smp_prepare_boot_cpu(void)
    > #ifdef CONFIG_KEXEC
    > static void kvm_crash_shutdown(struct pt_regs *regs)
    > {
    > - native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
    > +
    > + native_write_msr(msr_kvm_system_time, 0, 0);
    > native_machine_crash_shutdown(regs);
    > }
    > #endif
    >
    > static void kvm_shutdown(void)
    > {
    > - native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
    > + native_write_msr(msr_kvm_system_time, 0, 0);
    > native_machine_shutdown();
    > }
    >
    > @@ -181,27 +187,35 @@ void __init kvmclock_init(void)
    > if (!kvm_para_available())
    > return;
    >
    > - if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
    > - if (kvm_register_clock("boot clock"))
    > - return;
    > - pv_time_ops.sched_clock = kvm_clock_read;
    > - x86_platform.calibrate_tsc = kvm_get_tsc_khz;
    > - x86_platform.get_wallclock = kvm_get_wallclock;
    > - x86_platform.set_wallclock = kvm_set_wallclock;
    > + if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
    > + msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
    > + msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
    > + }
    > + else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
    > + return;

    Non conformant indentation.



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